Planning Poker integrates into the Trello board. You can estimate cards in the real-time with your colleagues and see estimation results on the cards. No Chrome extensions needed, this is a native cross-browser Power-Up.
Easy to use (hopefully)
Fully integrated into Trello board
Cards are pulled by the label
Estimates are displayed on the backs of the cards
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Developer: Vitalii Zurian
Price: Free for personal use, $2 per user per month with max at $50